Lactic acid bacteria (LAB) are a generic term of a class of bacteria with which large quantities of lactic acid can be produced from fermentable carbohydrates. This class of bacteria is widely distributed in nature, is abundant in species diversity, and has great application value in many important areas intimately related to human life including industry, agriculture and animal husbandry, food, medicines, and others. The use of lactic acid bacteria in food can increase the nutritive value, improve the flavor, and enhance the preservation and added value of the food. Also numerous studies suggest that the lactic acid bacteria may regulate the normal bacteria flora and maintain the micro-ecological balance in the gastrointestinal tract of an organism, enhance the digestion rate and biological value of the food, reduce the serum cholesterol, manage the endotoxins, inhibit the growth and reproduction of spoilage organisms and the production of spoilages in the intestine, produce nutritive substances, and promote tissue development, thus exerting an effect on the nutritional status, physiological functions, cell infection, drug effect, toxic reaction, immune response, tumor formation, aging process and sudden emergency response of an organism. As such, the physiological functions of the lactic acid bacteria are closely linked with the vital activities of the organism. It is believed that once cessation of growth of the lactic acid bacteria occurs, human beings and animals are hard to survive healthily. Accordingly, the lactic acid bacteria are widely used in a variety of light industries, food, medicine, and feed industry etc.
Pickles are typical traditional special fermented food in China, which are long in history, and deeply rooted in culture. Pickles have the effects of invigorating the spleen and increasing the appetite because they are tender, crisp, and refreshing, and have sour and sweet delicious tastes, thus being popular and favored by most of the consumers. Sichuan pickles are made mainly through fermentation with lactic acid bacteria, during which alcoholic fermentation, acetic fermentation, and other actions of organisms exist. The pickles are produced by cold processing, which is highly beneficial to the preservation of the nutritional ingredients, the color, and the flavor of the vegetables.
At present, the pickles are produced through conventional spontaneously inoculated fermentation or through pure culture fermentation by artificially inoculating Lactobacillus. The pickles produced through artificially inoculated fermentation are superior to those produced by spontaneously inoculated fermentation in terms of the improvement of the stability of the product quality, the shortening of the fermentation and production cycle, and the maintenance of the stability of the fermentation environment. However, if the tolerance of the start culture for artificial inoculation to the environment is insufficient, the color and flavor of the pickles and especially the number of the viable bacteria are affected. In Chinese Patent Publication No. CN 101720901S, pickles produced through fermentation with a starter culture and production method thereof, and more particularly pickles produced through fermentation with several pure lactic acid bacteria as starter cultures and production method thereof are disclosed. In the patent, the strains used for fermentation are Lactobacillus plantarum LP-115, Leuconostoc mesenteroides LM-57, and Pediococcus acidilactici P-751, which have a low tolerance to the environment, and tend to suffer from decreased number of viable bacteria during the storage and selling of the pickles, so that the healthcare functions of the viable bacteria cannot be highly exerted.
During the fermentation of the pickles, a safety problem that is difficult to overcome exists, that is, the production of the nitrite. Because the vegetables can easily accumulate nitrogen from the soil during growth, from which the nitrate is formed. The nitrate in the vegetables is reduced to form a nitrite during the process of anaerobic fermentation. The nitrite is very harmful to human body, poisoning may occur upon uptake in an amount of 0.2-0.5 g, and the nitrite is also a precursor of the highly carcinogenic substance nitrosamine. Therefore, there is a need for seeking a method for reducing the nitrite content in the pickles. In Chinese Patent Publication No. CN 102899262A, a Lactobacillus plantarum and a method for rapidly degrading the nitrite during fermentation by using the same are disclosed. In the method, the seed liquid of expanded Lactobacillus plantarum is inoculated in fermentation of Capsicum chinense, and 12% of high salt is added for flavoring after fermentation. The nitrite content in the Capsicum chinense fermented by using the method is significantly lowered, and the original flavor of the pepper is well retained. However, the salt content in the pepper is too high, and long-term consumption of the pepper may cause damage to human body.
Therefore, it is of great significance for the fermentation process of pickles to seek a starter culture for fermentation that has high acid production and high tolerance, and can reduce the nitrite content.